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Various types of simple separation on paper have been described as fore-runners of paper chromatography, among them a method of Runge in 1850, and the process called ‘capillary analysis’ (Goppelsroder, 1909). Such methods were really more like adsorption chromatography, and paper chromatography as it is now understood was a development of the partition system introduced by Martin and Synge in 1941 (see Chapter 2). One of the solids which can be used to support the stationary phase is cellulose powder (p. 38). Consden, Gordon and Martin[l] in 1944 separated the amino-acids and peptides in wool protein hydrolysates by a method in which the powder column was replaced by a sheet or strip of paper, freely suspended in a vapour-tight vessel.

Radioactive tracer techniques, coupled with chemical analysis by paper chromatography, became important in biochemical research in the late 1940’s, and today many investigations into intermediary and other aspects of metabolism rely on these methods. Soon after the marriage of chromatography to the use of tracers, various instruments were constructed which were able simultaneously to locate the positions of radioactive compounds on paper chromatograms and to determine the amount of radioactivity in each separated compound. Such devices are now available commercially in many different designs, and are intended for the scanning and counting of one-dimensional chromatograms only.

Assay of C14-labeled compounds isolated from metabolic experiments has been greatly aided by the high counting efficiency of liquid scintillation spectrometers and the ease of preparing samples for such assay. Difficulties arise, however, in liquid scintillation assay of (A) compounds isolated on paper chromatograms and (B) protein, because it is not easily soluble in most scintillation mixtures. The present report deals with improved methods for liquid scintillation assay of C14-compounds isolated by paper chromatography and of C14-labeled protein.

It is now common to analyze a concentration profile obtained by electrophoresis or gas chromatography using Gaussian distribution properties. The theory of chromatography [1] suggested that a similar type of analysis might also be valid for paper chromatography. The present study indicated the validity of this analytical method in the particular case of paper chromatography, provided that certain precautions are taken [2]. We propose here to point out its essential features.

Determining the type and amount of organophosphate pesticide residue in food products is a complex problem, and one which concerns both the companies which manufacture the pesticides and the Governmental agencies which enforce their proper use.

Rare earth metals, in the range of 0 to 250 micrograms, have been extracted quantitatively from perchloric, nitric or hydrochloric acid solutions by strong acid ion exchange paper disks in the sodium ion form. After the exchange is completed, the ion exchange paper disk is placed in a rotating sample holder and the amount of rare earth metals exchanged is determined by x-ray emission spectrography. At the 10 microgram level, the accuracy has a mean error of 2% with a precision of 1.5% relative standard deviation. The procedure has been applied to Sc+3, Y+3, Ce+4, Pr+3, Nd+3, Sm+3, Eu+3, Gd+3, Tb+3, Dy+3, Ho+3, Er+3, Tm+3, Yb+3 and Lu+3.

The availability of oxygen throughout the brain is far from homogeneous, oxygen tensions varying 30 or 40 mm Hg within a distance of a few microns (1–4). However, the pO2 at a given micro-area of cerebral tissue is remarkably constant, and can be changed only through major alterations in blood supply or the composition of respiratory gases (1,4,10). We have defined the different processes arrived at maintaining the constant brain cell oxygen micro-environment as “oxygen autoregulatory mechanisms.”

With the advent of various types of chromatography, a wide choice of methods is now available for the resolution and isolation of amino acids in complex mixtures. For quantitative analysis, paper chromatography and ion-exchange chromatography are the methods of choice. One-dimensional rather than two-dimensional paper chromatography is preferred as a routine procedure, samples being pretreated with ion-exchange resins to obtain groups of amino acids. Reliable methods for the isolation of the amino acids in the brain after paper chromatography have been published (Gaitonde, 1961; Gaitonde et al., 1965; Robinson and Williams, 1965).

There are a variety of methods for qualitative and quantitative determination of lipoproteins. Electrophoresis has found broad application as a routine method on account of simplicity as compared to ultracentrifu-gation. Thereby, serum lipoproteins are separated into various bands: alpha-, β-, pre-β-lipoproteins and chylomicrons and the relations of these bands to each other are visualized. In addition to the use of agar (URIEL and GRABAR, 1956; PEZOLD, 1957, 1958) and Reinagar (HOUTSMULLER et al., 1964) as supporting medium paper electrophoresis according to JEHCKS and DURRUM (1955) as modified by LEES and HATCH (1963) has been most commonly used, particularly since EREDRICKSON and LEES (1965) have recommended paper electrophoresis for differentiation of hyperlipidemia. Although paper electrophoresis permits demonstration of typical lipoprotein patterns for various types of hyperlipidemias, it is unsatisfactory with regard to the duration of 16 hours, and the frequent occurrence of poor separation particularly for pre-β- and β-lipoproteins.

Considerable technological progress has been made in the radioassay of analytical and preparative thin-layer chroma­tography (TLC) plates since Mangold’s original review of this subject (a chapter in Stahl’s book, Dunnschicht-Chromatog­raphic, 62–79, 1962). Although the general approach to radioassay of thin-layer chromatograms is similar to that used in paper chromatography, the two techniques require different radiometric procedures because the physical and chemical nature of the materials used in adsorption TLC are completely different from those encountered in partition separations by paper.

Chromatography on thin layers of loose adsorbent was carried out as early as 1938. Ten years later Meinhard and Hall used cohesive films which could be made to stick to a glass plate for chromatographic separations (1). With the introduction of paper chromatographic methods the separation and identification of complex mixtures of amino acids became possible. Following the initial work of Consden, Gordon, and Martin, in 1944 (2), paper chromatography of amino acids developed rapidly. Techniques were devised which permitted semi-quantitative measurement of all amino acids in a complex mixture, whether known or unknown. Development of thin-layer chromatography of amino acids lagged somewhat compared to techniques for separation of lipophilic substances, partly because of the highly satisfactory separations obtained by paper chromatography. However, most of the procedures applicable to paper chromatography were found suitable for use with thin-layer chromatography (TLC).

It is not possible in a short paper to describe the entire fossil fuel technology in any detail. However, for completeness, many of the more commonly used recovery techniques as well as some novel but untested methods are briefly described herein.

Enzymes attached to insoluble supports offer some particularly attractive advantages for many purposes including their use in the food processing industry. These advantages include repeated reuse of the enzyme, ease of removal from the reaction mixture, good or improved enzyme stability and properties which permit use in columns and large continuous reactors. In order to be successful an application must meet these criteria; in addition the costs for the support, the enzyme, the process for attachment, the equipment, and the operating costs must all be low. Previously we have reported on the use of phenol-formaldehyde resins as supports for immobilizing enzymes (1). This paper presents some of the most recent findings with this method of immobilization from pilot scale runs using a β-galactosidase from Aspergillus niger as the model enzyme for the hydrolysis of lactose in milk, whey, and deproteinized whey. Some examples of the variations possible with this method of enzyme immobilization are also discussed.

The heterogeneity of lactate dehydrogenase was first recognized when Neilands (1952) demonstrated activity in each of the two electrophoretically distinct proteins, previously separated by Meister (1950) from the crystalline ox-heart enzyme. Subsequently Vesell and Bearn (1957) found three distinct components when human sera were subjected to starch-block electrophoresis, and Sayre and Hill (1957) obtained similar results with paper electrophoresis and gradient-elution chromatography. About the same time Wieland and Pfleiderer (1957) found that most organs contain up to five protein fractions each exhibiting lactate dehydrogenase activity. Soon afterwards it was appreciated that the isoenzyme composition of the serum was of considerable diagnostic value (Vesell and Beam, 1958a, 1958b; Hess, 1958; Wieme, 1959), and this gave a tremendous impetus to further study of variations in the isoenzyme content of the blood serum.

The form in which acids are present in the analyzed material is important to the analyst: whether they are free, in aqueous solution, in the form of salts or solutions of these salts, or mixed with other neutral or acid substances. The character of the sample determines the course of the analytical procedure. It is also important to bear in mind that some carboxylic acids are volatile (lower aliphatic monocarboxylic acids), some are volatilized by steam distillation (monocarboxylic acids), others are water soluble (lower monocarboxylic and certain dicarboxylic acids), and practically all are soluble in 5% sodium hydrogen carbonate. All these properties offer a possibility of separating these substances from others. As carboxylic acids do not give characteristic color reactions, all general detections of this class of substance are based on their acidity. This is determined in aqueous solutions by means of indicators, and in the case of water-insoluble acids on the basis of their solubility in 5% sodium hydrogen carbonate. In all instances, however, it is advisable to complete the proof of acidity by titration with alkali; in the case of pure acids by determining their NE (neutralization equivalent), which is characteristic for each acid. In the case of more complicated mixtures titration affords information on the approximate amount of acids present in the sample and whether they represent a substantial fraction of it. If acidity is found in the sample, it is also necessary to look for the presence of sulfur, because the acidity could be caused by the presence of sulfonic acids. However, as the detection of acidity need not be reliable in more complicated cases, it is much safer to employ paper chromatography and to carry out the acidity detection on the chromatogram. This method has the advantage that it can also be carried out with salts.

X-ray fluorescence techniques combined with very simple procedures of sample preparation such as drying of a few droplets of liquid on filter paper allow measurement of calcium, potassium, chlorine, sulfur, and phosphorus in blood serum and in cell fluids. X-ray fluorescence is often more accurate and considerably faster than other analytical techniques. The hemoglobin contents of the blood may be determined by measuring the fluorescent intensity of the associated iron in the hemoglobin. In the case of toxicologic tests, the bromine content of blood serum, urine, and of cells or spine fluids may be determined reliably. Ashes of tissue, serum, and bones may be tested for heavy elements such as iron, zinc, copper, and strontium, and the calcium-strontium ratio may be determined. X-ray fluorescence further allows one to determine the sulfur content in electrophoretically separated protein fractions of the serum and to detect pathologic changes. X-ray fluorescence analysis further allows the determination of contents of specific and biologically effective substances as long as they are associated with a heavy metal. Examples for these determinations are cobalt-containing vitamin B12, iodine-containing hormones, or zinc-containing substances.

During the past few years several methods have been developed for the measurement of plasma testosterone. Finkelstein et al. (1) reported a method based on the enzymatic conversion to estradiol of testosterone isolated by paper chromatography. The estradiol was estimated by fluorometry. Double isotope derivative techniques using either H-acetic anhydride (2) or S-thiosemicarbazide (3) have been described. Although remarkable in their sensitivity and reproducibility, these methods are extremely complicated and expensive.

In our rheumatism research unit we are interested in the excretion of unconjugated corticosteroid metabolites because they may provide some evidence of the extra-hepatic metabolism of corticosteroids. A method was developed for estimating Cortisol metabolites in urine (1) which involved a preliminary separation of the extract by paper chromatography (Bush B5 system) and, after bismuthate oxidation, determination by GLC on a neopentyl glycol adipate column. This communication describes an improvement on the method and involves the following procedure.

Liquid chromatography has an impressive history, stretching back into the 19th century, which has been well documented elsewhere(1). As an indispensable technique for the separation and analysis of organic substances it has made enormous strides in the past decade or so. Prior to 1958 column chromatography was conducted with comparatively large samples separated in, often short, almost invariably wide-bore, columns through which the developing liquid percolated under gravity. Thin-layer techniques were unknown outside a small group of workers(2), although paper chromatography was widely practiced.

In the manufacturing of TNT, there are three waste water streams that must be processed in order to comply with federal and local government regulations. These are: (1) “red” water which is produced by the sellite (sodium sulfite) treatment; (2) “pink” water which is produced when the partially purified TNT is washed following the sellite treatment; and (3) wash waters from the TNT finishing process. While all these polluted streams are being investigated at the U. S. Army Natick Laboratories, this paper will cover results obtained with wash waters from TNT finishing processes.

Strips of Kodirex-X ray film, immersed for a few minutes into the chosen buffer, then quickly blotted between two sheets of filter paper, have been used as a supporting medium for the electrophoretic separation of various radioactive ions. After the electrophoretic run, the film strip was dried and stored in the dark until developed. Autoradiographic electrophoresis has been carried out with sulfate, taurine, taurocholate-35S, tritium-labeled succinic acid, histidine, glutamic acid-14C, tritium-labeled valine, and methionine. The separation of glutamic acid, histidine -14C, and tritium -labeled valine has been achieved at pH 7.25 and 5.25 (20 to 30 volts per centimeter for 60 min) (Fig. 1). The use of glucose-14C has shown that the nonelectrophoretic migration due to electro-osmosis and evaporation is negligible at the two above pH values (Fig. 2). The separations are sharp, the diffusion is weak, and unless the specific activities are very high, radioactive ions have no time to leave any track as they move in the photographic gelatin.

Laboratory, pilot and large field demonstration units were used concurrently to develop engineering design factors for concentration treatment of four different pulp and paper industry waste streams by reverse osmosis. Eleven, half-inch diameter tubular modules with cellulose acetate membranes were operated in parallel under closely controlled conditions of flow rate (to 5 1/2 gallons/minute per module); velocity (to 9 feet/second); concentration (tap water controls to 10% waste liquor solids); pH (2.5–7.5); temperature (20°C to 40°C); viscosity (0.8–2.0 cp); and time of continuous operation (to ten days/run). Detailed data obtained include turbulence (N Re ); viscosity; osmotic pressure; pressure drop; permeation resistance; and effect of reverse osmosis in terms of rejections of dissolved solids, BOD, COD, and Color (OD) for the individual wastes processed. Design factors developed from these data include pumping energy per unit volume; hydrolysis rates on cellulose acetate; concentration polarization; fouling rates by microbiological growth and other surface accumulations; and membrane compaction rates. Auxiliary information is being developed from these studies to provide a firm base upon which methods of pretreatment and of operation can be developed to maintain sustained operation with minimum membrane fouling and also methods and routines for systematic cleanups where required.

Owing to the greater sensitivity of the ionization detectors, when compared to general staining techniques in paper chromatography and other procedures, one can demonstrate that virtually none of the steroids available as commercial standards produce single peaks. In most instances this is simply a reflection of the presence of a small amount of impurity, rather than decomposition during chromatography. This can be ascertained readily by trapping the main peak and re-injecting into the gas Chromatograph. In a number of instances we have examined commercially available steroids in this manner and have found that only a single peak is obtained following this procedure. Almost none of the commercial steroids can be considered gas chromatographically pure. In some instances it has been quite easy to detect substances with retention times identical to those expected as by-products of the chemical reaction necessary to prepare the standard, or as biological companions where the steroid was obtained through extraction from natural sources. Indeed, the reader must be very cautious in the interpretation of the notation “chromatographically pure.” This, to our knowledge, never refers to “gas chromatographically pure.”

Gas chromatography and the electron-capture detector were used analytic procedure for the polynuclear hydrocarbons. Each fraction was collected for subsequent spectrometric analysis. A fraction collector designed by Packard Instruments, Inc., was used. The results by gas chromatography were found to be as good as or better than those by paper chromatography.

Chlorination of benzene was one of the first manufacturing processes for an organic chemical to be carried out industrially. Production was started in England in 1909 by the United Alkali Company (now part of Imperial Chemical Industries Limited) [1] and in the United States in 1915 by the Dow Chemical Company [2]. Up to that time the ‘heavy’ chemical industry had been mainly concerned with production of inorganic chemicals, particularly acids and alkalies. Widespread introduction of manufacture of sodium hydroxide by electrolysis of brine led to production of large amounts of chlorine for which, at that time, there were no commercial outlets, particularly as manufacture of bleaching powder was becoming obsolescent. Petrochemicals were still a thing of the future and the only organic raw materials which were available in large amounts were those derived from coal-tar, such as benzene. It was thus logical to look to chlorination of these products as a possible profitable use of the excess of chlorine to which industry was irrevocably tied as a result of the natural association of one atom of sodium with one atom of chlorine.

Lake and stream pollution remains a major national concern. New regulations, either now in effect or to be imposed in the next few years, will limit severely the amount of solids that industry and municipalities can discharge into natural waters. Among the industries affected are those either manufacturing starch or using it in processes where some starch may get into waste streams. Because dilute starch solutions suspend other solid materials, they constitute a problem in waste treatment.

The theory of origin of life on the Earth formulated by A. I. Oparin more than 50 years ago for the first time raised a problem of a possible abiogenesis of organic substances in the early period of the Earth’s existence.

The chief aim of the usual methods for eliminating styphnic acid from plant effluents resulting from the manufacture of lead styphnate is to avoid explosive hazards. They are based on the destruction of styphnic acid, either by oxidation or by reduction. Their main disadvantage is the formation of toxic reaction products and the toxic reagents added in some cases.

Poly(tetrafluoroethylene) (PTFE) is unique among polymers in its ecological position. Although there has been considerable discussion on recycling waste polymers such as poly(ethylene) (PE), poly(styrene) (PS), and poly(vinyl chloride) (PVC), only poly(tetrafluoroethylene) has been recycled in quantities significant compared to production. Over fifty times more PE is consumed in the form of trash bags for waste disposal than PTFE manufactured. Further, the growth rate of PE, PVC, and PS is continuing at 5–10%o per year while PTFE growth has plateaued. On a tonnage basis, then, the recycling of PTFE appears anomalous. The discrepancy disappears when the economic reward of reprocessing a $2.75/1b material is contrasted with that of a $0.14/1b material. The high scrap value of PTFE provides an incentive for both fabricators and end-users to accumulate waste in reasonably concentrated bulk. Further, freight cost to reprocessing installations is not a significant portion of the polymer cost. Due to the economic incentive a wide variety of methods for up-grading waste PTFE to reprocessable grades have been evaluated. The techniques employed may be transferable to other polymers of greater ecological impact.

Ethylene oxide (ETO), an alkylene oxide, has been used for many years to kill microorganisms and insects (1,2). The principle use in the past has been the fumigation of foodstuffs and spices; ethylene oxide is still used extensively in agricultural industries for this purpose (3). During the last 20 years the effect of time, temperature, relative humidity, and concentration of ETO on sterility has been repeatedly discussed (4,5,6,7,8).

Within the last 3 yr. there has been a very rapid increase in the usage of urea as a high grade fertilizer, animal feed supplement, and raw material for certain resins. The low-cost production of urea in large quantities has been widely studied by chemical engineers, and a number of processes have been developed, both in this country and abroad, which reflect considerable sophistication in engineering technology and in the use of specialized alloys to meet the corrosion problems encountered in the reactions required to produce urea.

It has been known for some time that certain Ascomycetes and Fungi Imperfecti are capable of attacking cellulose and nonlignified materials. For instance: 1. A great many can attack cellulose plant fibers such as cotton, causing serious destruction of fabrics. 2. Others may grow through wood, living on stored food materials, such as starches and sugars in the ray cells, and thereby stain and discolor the wood. 3. Others not only utilize the food material within the ray cells but also the pectin and hemicelluloses of the walls. When the cells are dissolved, porosity is increased, and the wood becomes more absorptive of water and preservatives. It is of interest to note here that certain bacteria also are capable of dissolving the ray cells in logs stored in ponds for the purpose of preventing stains and decay (Ellwood and Ecklund, 1959). Increased absorptiveness may cause considerable drying and paint-maintenance problems. Increased porosity in wood can, on the other hand, be of value to the wood preserver. In experiments directed toward improving the penetration of preservatives, chemicals, such as sodium fluoride, have been sprayed on logs to stimulate the growth of molds, particularly Tricho-derma (Lindgren, 1952). 4. A few bark-inhabiting Ascomycetes are known to decay small branches and twigs. Their attack on the lignified walls of tracheids, vessels,and fibers, however, has been regarded as unimportant.

Oxidation ponds are one of the common methods for stabilizing domestic and industrial wastes, and are used widely in many countries. They have become one of the most accepted solutions for treatment of wastes in Israel and a large-scale project, the “Recovery of the Dan Region Wastewater”, is in operation in this country.

Two main groups of procedures are available for the separation of isoenzymes, namely electrophoresis and ion-exchange chromatography. Both depend primarily upon the nature and extent of the resultant charge on the protein fractions in the buffer solution used. For analytical purposes several micro-electrophoretic techniques can be used, but when it is required to separate isoenzymes on a preparative scale chromatographic methods may sometimes be more convenient. Before discussing the various procedures which can be employed, brief consideration will be given to some of the factors to be taken into account in the preparation of enzyme solutions.

Pesticide manufacture normally yields a crude synthetic product which can be purified or refined to a specified content of the active ingredient. The major concern of the analyst is to define the amount of active ingredient present in formulations or batches of technical material from the plant. Contaminants have rarely given cause for concern, since biological testing with technical material might be expected to reveal the presence of impurities with significantly different properties from the active compound. For example, the selectivity of the herbicide amiben (3-amino-2, 5-dichlorobenzoic acid), is reduced by the presence of 2,5-dichloro-6-nitrobenzoic acid or 6-amino-2,5-dichlorobenzoic acid and crops are damaged by these compounds. Because these two compounds possess undesirable biological activity, they must be removed by rigorous control of the manfacturing process (H. Segal, 1967).

This section contains the title and contents of 98 of the more relevant textbooks published in the field of industrial microbiology. All but 12 of the books have been published since 1960.

The development of reverse osmosis as a process for desalting brackish and seawater originated with the research of Reid and Breton at the University of Florida in 1954–1956. These investigators showed that cellulose acetate film is capable of separating salt from water by reverse osmosis, although at a very slow rate. Soon after this, Loeb and Sourirajan at the University of California developed a unique process for making an asymmetric or “skinned” cellulose acetate membrane. The water flux and salt rejection of this membrane were sufficiently high to make the reverse osmosis process an attractive candidate for desalination. Just ten years later, small capacity commercial reverse osmosis units were available to the public.

The trend toward tougher anti-pollution standards has had a tremendous impact on the coatings industry. In the recent past, research and development efforts have been directed toward new coatings or coating methods which can fill existing customer needs while eliminating the associated pollution problems. Much of that effort has been or is going into water based coatings. The principal advantages and disadvantages of water based coatings over conventional organic systems are tabulated below. In the past, the higher heat input and longer flash-off time generally required for water based coatings may have hindered the growth of these systems. In addition, water based systems were found to be slower curing. To overcome these drawbacks, new developments in polymer systems and cross-linking agents were needed. In the late 1960’s water soluble, fast-curing, partially methylated melamine resins were introduced and found immediate acceptance in water- and solvent-based systems. With the subsequent development of methylated urea formaldehyde cross-linking agents, however, even faster curing speeds are now obtainable.

In the past several years there has been a continual increase in the use of ultrafiltration (UF) membranes for concentrating, separating, and purifying various dissolved solutes. The forecast in membrane separation processes as reported by Pattison (1968) will amount to $7.5 million by 1975. Of this total, it was estimated that $37.5 million will be spent in UF processes for industrial, medical, and surgical operations. Parallel in time with membrane-technology development is the increased usage of various enzyme preparations. Specifically, the use of enzymes in laundry detergents has caught the fancy of housewives in the past 2 years. Although the enzyme industry in the United States is by no means new, the recent innovation of enzyme additives in detergents has contributed significantly to the total market. For example, the total U. S. enzyme market in 1968 amounted to approximately $40 million, of which approximately $9 million was for laundry products (Anon., 1969A). However, the latter is expected to increase to $25 to $30 million in 1969 (Anon., 1969B).

Decay in Nature. The principal external agents of decay or destruction in nature are erosion, corrosion, oxidation, thermal expansion and contraction, enzymic action, the growth of microbes and moulds, and attack by predators. Also, living organisms have their own life cycles—they “age and die and heaven knows why.” The remedies against physical damage and chemical action (of which oxidation is a special case) are straightforward in principle, if sometimes difficult to apply: so also is protection from predators. Enzymes are inactivated by heat which can also destroy microorganisms. Both are also vulnerable to changes in electrolyte and hydrogen ion concentration (pH), freezing, drying, and irradiation. Pickling in vinegar is a combination of heat and pH change. Jam making combines heat and dehydration because the sugar reduces the available water. But suppose it is the bacteria, yeasts, moulds, and viruses themselves that we wish to preserve—any method that destroys them is immediately excluded.

Several years ago it became apparent that uridine nucleotides containing various carbohydrate moieties were the probable precursors of polysaccharides. This observation followed largely from the initial work of Leloir and his collaborators [1] and of Park [2]. Work by Cifonelli and Dorfman [3] showed that Group A streptococci contain UDP-glucuronic acid (UDPGA), UDP-N-acetylglucosamine (UDPAG), and UDP-N-acetylmuramic acid. The first two, UDPGA and UDPAG, contain the constituent monosaccharides of hyaluronic acid (HA), an acid mucopolysaccharide that occurs in connective tissues and in the capsule of certain Group A streptococci. Although reasonable quantities of the nucleotide precursors of HA were available, labeling with C14 would have been both difficult and time consuming.

In developing the proposed method, the author attempted to find suitable methods of obtaining air-dry and improved wood for industrial purposes with the help of simple devices.

Until recent years, water treatment by ion exchange was considered as a largely inorganic process and resins were judged solely by their ability to exchange or remove mineral ions. The total organic content of natural water supplies is considerably lower than the inorganic content, and when the standard of water purity required for industrial purposes was 1–2 μS/cm (S = mhos), organic contamination of the input water was rarely sufficient to cause noticeable changes in the quality of the treated water, or the apparent working capacity of the resins. The greater purity requirements of modern boilers, necessitating conductivities of down to 0·1 μS/cm, have converted into severe problems phenomena which were virtually unrecognized until the 1950’s. The nature of the problem is best illustrated in Figure 37 which shows typical results of mixed bed operation under a number of conditions. If the input water contains no organic matter, then results such as Curve B arc readily obtainable, and under ideal conditions, the treated water quality can be as good as in Curve A. Typical results for London water, a mixed and variable supply with about 300 p.p.m. T.D.S, and 1–2 p.p.m. O.A, are given in Curve C, while old mixed beds which have become poisoned will do no better than Curve D. Indeed, some of the thin, organic-loaded waters occurring for example in Wales will rapidly foul a conventional mixed bed to a much greater extent, the conductivities being around 2–3 μS/cm.

The title of this paper is listed as “The Use Of Thermal Evolution Analysis for the Determination of Vapor Pressures of Agricultural Chemicals ”. The phrase “agricultural chemicals” includes an extremely broad range of chemicals including insect repellents and att-ractants, herbicides, pesticides, fertilizers, and many other products. Such a broad field would be extremely difficult to cover in the space of this paper and so I will, of necessity, limit my remarks to one, much smaller area, that of insect repellents. The techniques used in this study are perfectly general, however, and I leave it to the imagination of the reader to extend this work to the general case.

The industrial microcapsules first disclosed in the patent literature in 1957 are prepared as microscopic containers of oily material (1). These microcapsules containing oil are coated on paper. Mechanical pressure rupture these microcapsules, releasing their oily content to form prints—the basis of the well-known NCR carbonless paper. Since then, most of the industrial and pharmaceutical microencapsulation technology are similarly prepared to contain medication, fuel, perfumes, adhesives, and others. In all cases, the enclosing wall of these microcapsules are made as impermeable to external and internal molecules as possible, and the enclosed material can act only when the microcapsule wall is disrupted releasing the enclosed material. The enclosing walls are, therefore, rather thick (greater than 1 micron).

This paper is concerned with the flow of heat in the low-field mixed state of two single crystals of niobium: Nb4, of resistance ratio about 300; and Nb5, of resistance ratio about 1300. In the temperature range covered, 0.4–1.2°K, heat flow in the Meissner state of these crystals is due entirely to phonons.1 Preliminary measurements on these crystals have already been reported by us2; in the present paper we report certain aspects of our latest results that are of particular interest. A full account will be published elsewhere.

Using a novel DTA technique, it has been reported that polyethylene (PE) single crystals exhibit narrow multiple-peaked thermograms1. The half-width of the individual peaks is usually less than 1.5°C. These peaks widths are comChapauble to those obtained using pure non-polymeric organics. Previous work suggested that discrete transformation temperatures exist for the {100} and {110} fold sectors2. The work that led to this suggestion was performed on lamellae produced by isothermal crystallization from a dilute (.1%) solution of PE in xylene. The solution was heated to the boiling point of xylene prior to being quenched to a particular crystallization temperature. Several questions evolved from this latter paper. The first of these concerns the homogeneity of lamellae produced in this way. Since not all lamellae began to crystallize at the same time, a distribution of sizes appears. Crystals often possessed overgrowths and/or defects. One might also question both the heating rate effects reported and the justification for resolving multiple-peaked thermograms into discrete components. It is the object of this paper to attempt to answer these questions.

In a previous paper (1) we had already reported results on the erasure by an ac field (1 KHz) of the texture stored in nematic-cholesteric mixtures by application of a dc field. The decay of the scattered light intensity after the dc field removal can be characterized by an erasure time τE defined as the time during which this intensity falls from 90 to 10 per cent of its initial value. This time can easily be determined and the variations of τE with various parameters have been examined for mixtures of negative dielectric anisotropy consisting of a commercial product (LCI), nematic in the range 5–70°C and of cholesteryl nonanoate (CN). The experimental results showed that the time τE decreases when the temperature increases (following a law similar to that of the pure nematic substance)and also when the erasing ac voltage rises, the greater the concentration the faster the decrease. In this paper we have studied in more detail for the same mixtures, the variations of the erasure time τE (for 1 KHz) with the dc voltage producing the storage effect.

Backscattering techniques allow determination of elemental composition as a function of depth with typical values of depth resolution of 100 to 300A. The technique is ideally suited to measurements in thin film systems of thicknesses of several thousand Angstroms and has provided a basis for examination of thin film interactions. This presentation is intended as an introduction to the papers presented in this session of the conference. These papers represent examples of the type of studies carried out in this field: interdiffusion and mixing between thin metal films, and reaction kinetics and silicide formation in systems composed of metal films deposited on Si or SiO2. These studies involve solid-solid diffusion and reactions since the process temperatures are below the eutectic. Although backscattering techniques provide depth-microscopy, supplemental measurements are often required to establish lateral uniformity and the relative importance of grain boundary and bulk diffusion.